eLORAN Signal

The principal difference between the eLORAN transmitted signal and the traditional Loran C signal is the addition of a data channel. The data channel conveys corrections, warnings, and signal integrity information to the user's receiver via the Loran transmission. The data transmitted may include:

• The identity of the station; an almanac of Loran transmitting and differential monitor sites;
  
• Absolute time based on the Coordinated Universal Time (UTC) scale; leap-second offsets between eLORAN system time and UTC;
  
• Warnings of anomalous radio propagation conditions including early skywaves; warnings of signal failures, aimed at maximizing the integrity of the system;
  
• Messages that allow users to authenticate the eLORAN transmissions; official-use only messages;
  
• Differential Loran corrections, to maximize accuracy for maritime and timing users; and
  
• Differential GNSS corrections.

eLORAN transmissions are synchronized to an identifiable, publicly-certified, source of Coordinated Universal Time (UTC) by a method wholly independent of GNSS. This allows the eLORAN Service Provider to operate on a time scale that is synchronized with but operates independently of GNSS time scales. Synchronizing to a common time source will also allow receivers to employ a mixture of eLORAN and satellite signals. Phase corrections are provided in a continuous vice stepped manner.

Users will continue to be notified immediately of signal outages and abnormalities. Scheduled maintenance work is planned carefully to minimize the impact on users of stations being off the air. Users are given adequate notice of interruptions via well-publicized channels of communication.

Users’ Equipment: eLORAN users’ receivers operate in an all-in-view mode. That is, they acquire and track the signals of many Loran stations (the same way GNSS receivers acquire and track multiple satellites) and employ them to make the most accurate and reliable position and timing measurements. Another benefit of using the all-in-view mode is that it ensures that the eLORAN receiver is always tracking the correct cycle of each individual signal.

An eLORAN receiver is capable of receiving and decoding the data channel messages and applying this information based on the user specific application (Figure 1). This information, coupled with the published Signal Propagation Corrections, provides the user with a highly accurate PNT solution.